From evolutionary point of view, retention of the female gametophyte with developing young embryo on the parent sporophyte for some time, is first observed in:

This phenomenon is a precursor to the seed habit. It was first observed in Pteridophytes, particularly heterosporous ones like Selaginella and Salvinia, where the zygote develops into the embryo within the female gametophyte while it is still attached to the sporophyte.